Reciprocator



May Z6, 1953 F. L. BAMFORD RECIPROCATOR Filed Oct. 16, 1950 INVENTOR.

FRANK L BAMFORD BY www @www ATTORNEYS Patented May 26, 1953 UNITED STATES PATENT OFFICEv RECIPROCATOR Frank L. Bal'nford, Detroit, Mich. Application October 16, 1950,? Serial No. 196,???v

I (Cl. 'I4-60) 6 Ciaims.

1 The invention relates to mechanisms for im.- parting rapid rectilinear reciprocations to a member thereof, being more particularly designed for use as a sanding tool.

It is the primary object of the invention toobtain a construction in which the inertial forces are so counterbalanced as to avoid deiiection of the reciprocating element from a rectilinear path.

It is a further object to obtain a very simple construction which can be manufactured at low cost.

Still further it is an object to obtain a construction in which the mass of the reciprocating elements is reduced to the minimum and is small in comparison to the mass of the whole tool.

With these objects in view the invention consists in the construction as hereinafter set forth.

In the drawings:

Fig. 1 is a side elevation of my improved mechanism designed for use as a sanding tool;

Fig. 2 is an end elevation thereof;

Fig. 3 is a longitudinal section through a portion of the mechanism illustrating the means for translating rotary into reciprocatory movement.

Any suitable motor may be employed as the driving element of my improved reciprocator but, as specifically shown and described, an electric motor of standard construction and preferably of fractional horsepower is used for this purpose. This motor is of cylindrical form and comprises generally a rotor and stator, but the specific construction forms no part of the instant invention and therefore is not illustrated or further described. f

As shown A is the rotor and B is a cylindrical stator surrounding the same and providing suitable bearings for the rotor (not shown). Arranged at opposite ends of the motor are lever members C and D which are centrally fulcrumed upon pivots E engaging ears or brackets F .projecting outward from and secured to the stator upon opposite ends thereof. The lower ends of these levers are pivotally attached to a reciprocatory member G, which as shown constitutes the sanding element. The upper ends of the levers are pivotally attached to a reciprocatory member H which forms a counterbalance for the member G. The member H is preferably of a segmental cross section so as to conform to the shapeof the cylindrical motor adjacent thereto. I is a casing or handhold member extending over the top and downward upon opposite sides of the motor and the member H, forming a shield for the latter.

To impart a rapid reciprocation to the members G and H and the levers C and D supporting the same, I preferably employ a wobble'mechanism J mounted on a projecting portion K ofthe rotor shaft which extends through a central aperture in the lever C. This wobble mechanism includes a member J keyed or otherwise secured to the shaft K and provided with an annular peripheral channel J2 which is in a plane oblique to the axis of the shaft. Surrounding the member J and the channel J2 thereof is an annular member J3 which has an internal channel J 1 complementary to the channel J2 and together therewith forming race members for a series of balls J5. J6 are pivot pins extending respectively upward and downward from the member J3 in the central plane thereof and engaging bearings in the lever C. Thus the rotation of the shaft K will impart an oscillatory movement to the member J which, in turn, will reciprocate the lever C through the medium of the balls J4, annular member J3 and pins J 6. The fulcrum pivots E hold the lever C and member J3 against transverse oscillation. Also these members form in eiTect an end thrust bearing connection between the rotor and stator.

The member G which forms the sanding element is provided With suitable means (not shown) for attaching the abrasive sheet thereto, the construction being made as light as possible so as to minimize the inertia thereof. The member H is of a mass to counterbalance the member G, the inertial forces in these members being equal and in opposite directions. The motor including both rotor and stator is necessarily of considerably greater mass which, however. is advantageous as it reduces displacement thereof by the reaction of the reciprocating elements G and H. Also the angular movement of the levers C and D is so small that the paths of the members G and H are substantially rectilinear. As the axes of the fulcrum pins E of the levers C and D intersect the axis of the rotor and center of mass of the motor any reaction forces communicated from the levers to the motor will be in an axial direction. Consequently, when the mechanism is in operation, the sanding element G will maintain its contact with the surface of the work and with little or no tendency to move out of the plane thereof. The casing I forms a handhold grasped by the operator by means of which he can advance the tool over the surface of the work.

While the motor in the above described construction is an electric motor, it is obvious that other types of motors such, for instance, as a pneumatic motor with suitable iiexible connections might be substituted therefor.

What I claim as my invention is:

1. A reciprocator mechanism comprising a rotor and a stator, a wobble mechanism mounted on said rotor including an annular non-rotating universally wobbling element, a lever, and pivotal connections between said lever and said annular member and stator respectively, the axes of said pivotal connections being transverse to each other and both intersecting the center of wobbling movement.

2. The vconstruction as in claim 1 in which the lever embraces said wobble mechanism, and both of said pivotal connections extend on diametrically opposite sides of said annular member with their axes in a common plane of the lever.

3. The construction as in claim 2 in which said lever together with its pivotal connectionl consti-v tutes an end thrust bearing between the rotor connection to the stator and has a member tojbel reciprocated connected to one end of said lever. and a oounterweight connected to the opposite end thereof.

5. The construction as in claim 4 in which said rotor and stator constitute cooperating elements of a motor with said wobble mechanism and said lever located at one end of said rotor, and a second lever fulcrumed on said stator at the opposite end of said rotor, said member to be reciprocated extending between and being pivotally connected to both levers. vL

6. The construction as in claim 5 in which both levers carry counterweight means.

FRANK L. BAMFORD.

References Cited in the file of this patent UNIIELIDH STATES PATENTS Name Date 2,236,738 Swenson Apr. 1, 1941 2,491, 6.24;I A Shari A Dec. 20, 1949 "2,513,083 -Eckert Lv June`27.' 1950 Number 

